I was reading through a site describing terraforming the solar system. What interested me most was the idea of turning jupiter into a small star and what would happen to its tidally locked moons, specifically Io. It describes Io as having a night/day/superday cycle on its dark side due to the other moons and the distant sun. What I'm curious about is if this would provide enough light/heat to the dark side of a similar system to allow some type of terrestrial and human life to exist without hand waving? (all other factors such as atmosphere,weather, gravity,etc notwithstanding)
Not if it was like our moon. I think you could create an artificial "moon" made of reflective material to heat up the dark side of a tidally locked planet far more plausibly. If we have space travel and the ability to colonize new planets, that seems within the realm of possiblity.
From moons? They have to be a lot more reflective than our moon is. Despite how bright it appears in the sky, it is about as reflective as a asphalt parking lot.
The amount of radiation you get is in ratio of the moon's radius to the moon's orbital radius squared. E.g. with a moon of radius 1000 miles, and an orbital radius of 100,000 miles then the light/heat will be diluted by (1000/100,000)^2 or about 1/10,000. And that is with perfect reflection.
Flat mirrors help. You can get some degree of directionality with the reflection.
Closer bodies help. More of the reflected light is collected by the planet.
Bigger bodies help. Jupiter takes up a lot more sky for it's innermost planet than the earth does for the moon.
How about a trillion Echo balloons?
I am not sure for that scenario but I have heard of plans to heat Mars up by using gigantic reflectors made using the same material as rescue blankets. By gigantic I mean hundreds of kilometers on a side. So if this is what we could do with technology, I am not sure if a moon can reflect AND focus enough infrared energy.